1. Field of the Invention
The present invention relates to a read-only recording medium and a reproducing method thereof. A read-only recording medium in accordance with the present invention ensures reproduction compatibility with a rewritable recording medium in which real-time data such as moving-picture and audio data is recorded with substantial discontinuity.
2. Description of the Related Art
A disk of large storage capacity, called ‘DVD’, which has been developed to store high-quality moving pictures for longer time than a compact disk (generically called ‘CD’), is expected to be widely used. The DVD has three types, ‘read-only’ such as a DVD-ROM, ‘write-once’ such as a DVD-R, and ‘rewritable’ such as DVD-RAM or DVD-RW.
The read-only type, namely, the DVD-ROM which is being widely used at present is a high-density recording medium and is 4.7 Gbytes in storage capacity. This capacity is about eight times as large as a conventional CD. The DVD-ROM has two recording areas for user data and management information. A real-time data, such as high-quality moving-picture data or audio data, has been recorded seamlessly in the data recording area, and management information such as navigation data for reproduction control of recorded real-time data has been recorded in the management information recording area.
FIG. 1 is a hierarchical structure of real-time data recorded in the data recording area of a DVD-ROM. The recorded real-time data shall be constructed with at least one video object (VOB) which is a data collection corresponding to a video title or chapter. The VOB shall consist of a plurality of video object units (VOBUS). Each VOBU shall consist of two ECC blocks each of which shall consist of 16 sectors. Because the size of a sector is 2048 Bytes the ECC block is about 32 Kbytes in size.
A disk device, such as a DVD player or a DVD drive, capable of reproducing a DVD-ROM reads the management information for recorded data from the management information recording area first, and then reproduces the real-time data structured as FIG. 1 from the data recording area with reference to the read management information. Because the real-time data has been recorded continuously, a seamless reproduction can be accomplished only if the real-time data is outputted in the order of reproduction without any special data manipulation.
In the meantime, the concrete standard for a rewritable DVD, such as a DVD-RAM or a DVD-RW, is under development. Such a rewritable DVD has the same storage capacity of 4.7 Gbytes as the read-only DVD-ROM.
Thus, if such a rewritable DVD is commercially and commonly used as a data storage means, a user can record desired digital television broadcast programs for a long time or copy real-time data stored in a DVD-ROM onto a DVD-RAM or a DVD-RW through a disk device like a DVD recorder.
As explained above, the real-time data has been stored seamlessly in a DVD-ROM. However, the real-time data is recorded discontinuously in the rewritable DVD because an area for header information or linking loss is allocated intermittently among real-time data.
FIG. 2 shows a data structure recorded discontinuously in a rewritable DVD-RW. As shown in FIG. 2, RMA (Recording Management Area) except RMA Lead-in is constructed with 5 RMA segments. Each RMA segment consists of 28 RMD (Recording Management Data) sets. Each RMD set consists of a plurality of 32-Kbyte RMD blocks each of which is constructed with 15 data fields and a linking loss area of 2 Kbytes in which valid real-time data is not to be written. Because a linking loss area is inserted at the head of every RMD block the data recorded in the DVD-RW is in discontinuous recording state.
Usually a linking loss area is provided for sufficient buffering for facilitating fully random write or overwrite.
Because of the linking loss area or the header information area in which valid data shall not be written, the substantial storage capacity of a DVD-RAM or DVD-RW is correspondingly reduced from the nominal capacity of 4.7 Gbytes. Thus, the entire data stored in a DVD-ROM can not be copied onto a DVD-RAM or a DVD-RW.
When a DVD-ROM is placed in a disk device, such as a DVD player or a disk drive, the disk device can reproduce real-time data stored in a DVD-ROM seamlessly by simply outputting data read from a DVD-ROM in reading order without any special manipulation. However, if a rewritable DVD-RW or DVD-RAM which data has been discontinuously recorded onto is placed in, a disk device must conduct a special operation to accomplish seamless reproduction, namely, it temporarily stores all data read from the rewritable disk, deletes data read from the header information or the linking loss area, and outputs real data before and behind the header information or the linking loss area. Accordingly, a disk device must be equipped with different reproduction algorithms which are selectively used based on the type of a placed disk.